1. Field of the Invention
The invention relates to an ozone generator comprising an outer electrode and a plurality of inner electrodes which have a dielectric coating on their outer surfaces, discharge gaps between the outer electrode and the dielectric coating, and an alternating current source connected to the outer and inner electrodes.
Ozonizers of this type are known, for example, from Swiss Pat. No. 648,534.
2. Discussion of Background
As a result of the increasing use of ozone for chemical and physical purposes, in the recent past the ozone tube which goes back to work done by us at Siemens has been decisively improved from the technical and economic point of view. Thus, it is proposed in U.S. Pat. No. 2,811,217 to enhance the ozone yield by requiring that specific characteristics of the ozonizer (frequency of the supply voltage, dielectric constant of the dielectric material, amplitude of the supply voltage, thickness of the dielectric coating and size of the discharge gap) fulfill specific regularities.
In other publications, special cooling measures are proposed for the same purpose in order to enhance the ozone yield, thus, e.g. alongside the liquid cooling of the outer electrode, internal cooling of the high-voltage electrode with gas or liquid in German Offenlegungsschrift No. 2,357,392, or intermediate cooling of the ozone-enriched gas employed in the case of series-connected ozonizers in German Offenlegungsschrift No. 2,436,914.
It is generally known that by reducing the discharge gap width in a tubular ozone generator the mean temperature in the discharge gap can be reduced. It can be shown theoretically and experimentally that the mean temperature in the discharge gap is proportional to its gap width. A low temperature in the discharge gap is desired because in this way the efficiency of the ozone generation can be markedly improved.
Today, discharge gap widths of around 1 mm are prior art. A further reduction of the gap width comes up against the geometrical tolerances of the metal tubes and dielectric tubes which are employed. Especially with sizable tube lengths, a further reduction in the gap width is limited by the always present flexures of the dielectric tubes and metal tubes.
With the aim of enhancing and rendering uniform the intensities of the field strength, it is proposed in German Offenlegungsschrift No. 3,422,989 to form the inner electrode as a solid metal rod. Because the diameter of the rod is small by comparison with a tube, the field strength at its surface is high. Since, in addition, the diameter of the outer electrode is correspondingly diminished and low material thicknesses are employed, the result is an elastic construction. The distance between outer and inner electrode and dielectric can be maintained very precisely over the entire length. The result of this is uniform intensity of the field strength, good cooling possibilities, compact construction and high power.